Laminated core and method of producing laminated core

ABSTRACT

Thin sheets of magnetic material are subjected to a pressing process to stamp many sheets of core pieces, and caulking projections defined in the core pieces are caused to go into connecting through holes defined in the core pieces for connecting and laminating to produce a laminated core. In lower layer of the core pieces having the caulking projections arranged in different positions seeing in plan, at least two sheets of core pieces and other core pieces having the connecting through holes are provided. The caulking projections defined in the core pieces have projecting length of at least twice of thickness of the core pieces, and are fitted in the connecting through holes, so that upper and lower laminated core pieces are unified.

TECHNICAL FIELD

This invention relates to a laminated core made by laminating thinsheets having magnetism (for example, silicon steel sheet), and a methodof producing the same. Herein, the laminated core is used to, e.g.,rotors or stators of electric motors.

BACKGROUND OF THE INVENTION

Conventionally, for heightening output of motors, or attaining smallsize, light weight and high performance of the same, rotor cores orstator cores have been applied with laminated cores of predeterminedthickness made by laminating many core pieces punched from thin steelsheets by pressing works. When laminating many sheets of thin corepieces, caulk-connection portions such as a V-shaped projections or acut-and-rising portions (or embossed projections) are provided per eachof core pieces, and core pieces are caulked one another viacaulk-connection portions and laminated one another.

However, if thickness of the core piece is, e.g., less than 0.2 mm, atthe caulk-connection portion such as the V-shaped projections or thecut-and-rising portions, length for connecting upper and lower cores istoo short, it has been difficult to realize enough caulking strength.Therefore, since the caulking strength between the respective corepieces composing the laminated core is low, problems have been involvedwith assembled laminated core being peeled or caused with poor shape.

The invention has been made in view of these circumstances, and it is anobject of the invention to provide a laminated core which has thecaulk-connecting strength though core pieces have thickness of less than0.2 mm, and causing neither peel nor poor shapes, and a method ofproducing the same.

DISCLOSURE OF THE INVENTION

The laminated core according to the invention for satisfying the abovementioned object comprises: core pieces formed with caulking projectionshaving length projecting at least twice of thickness of core pieces, andat least two sheets of core pieces respectively laminated under saidcore pieces formed with said caulking projections and formed withconnecting through holes for fitting said caulking projections, and saidcore pieces which are formed with said caulking projections are formedwith parts (namely, lower connecting holes, punched holes) of theconnecting through holes for fitting the caulking projections of uppercore layers at places which are different from places forming thecaulking projections formed in the core pieces, that is, connected withthe cores laminated thereon. It is possible thereby to secure thickness(length) of the connecting through hole for fitting the caulkingprojection. The core piece at the bottom of the connecting through holefor fitting the caulking projection may be a core piece at a still lowerposition than the core defined with the caulking projection at a placeof a subsequent lower layer. The laminated core is made yet strongerthereby.

In the laminated core according to the invention, it is preferable thatthe caulking projection has a base portion reducing the width as goingin a front end direction, and, among the connecting through holes formedin said plural core pieces, the connecting through hole of the corepiece immediately under said core piece formed with the caulkingprojection has the width widening than said width of said caulkingprojection. Thereby, the caulking projection easily goes into the coreimmediately under the core piece defined with the caulking projection,and after the core piece goes a little thereinto, the connecting throughhole (the upper connecting hole) of the core piece is a guide for thecaulking projection.

In the laminated core according to the invention, it is preferable thatthe connecting through hole formed in the core piece is partiallydefined at circumference with concaves. Thereby, the caulking projectionpartially goes into the core piece, and the caulking strength increases.

In the laminated core according to the invention, it is preferable thatthe concaves are two or more, and the respective concaves are definedsymmetrically with respect to the axis of the connecting through hole.Thereby, the caulking projection is difficult to generate displacement,and as a result, the core pieces cause no divergence in lamination.

In the laminated core according to the invention, it is preferable thatthe caulking projection is shaped as nearly trapezoidal or nearlymulti-trapezoidal viewing from the side thereof. Thereby, the corner ofthe caulking projection does not bite into the connecting through hole,or no twist is generated in the caulking projection. In this case, theopposite two sides of the caulking projection may be separated from thecore piece, or all the side walls of the caulking projection may beseparated from the core piece.

In the laminated core according to the invention, it is preferable thatthe caulking projection has a front end portion widening the width owingto pressure. Thereby, the caulking projection and the connecting throughhole are caught accurately.

A method of producing laminated cores according to the invention, issuch a method where caulking projections and connecting through holesare formed in many sheets of core pieces punched in magnetic thin sheetsby a pressing apparatus, and caulking connection is performed whilelaminating these core pieces, and comprises: an A step of punching theplural sheets of core pieces formed with the connecting through holes inthe magnetic thin sheets by means of the pressing apparatus, a B step offorming caulking projections passing until the bottoms of the connectingthrough holes formed in the plural sheets of core pieces laminated inthe precedent step, and laminating core pieces formed, in upper places(i.e., places of the upper layers), with punched holes forming parts ofconnecting through holes for fitting new caulking projections formed inplaces different from those of said caulking projections, and a C stepof laminating core pieces formed with punched holes to be parts of theconnecting through holes formed by meeting axes to said punched holes ofsaid core pieces laminated in the B step, and forming plural sheets ofcore pieces defined with the connecting through holes together with saidcore pieces laminated in the B step, wherein the B step and the C stepare repeated to form the core laminated at a predetermined thickness insaid B step as a final process. Thereby, it is possible to produce thelaminated core by use of the pressing apparatus, changing places, wherethe caulking projections bite into a plurality of core pieces, in thelaminating direction neighboring in the vertical direction (namely, notto overlap).

In the method of producing the laminated core according to theinvention, in the B step as said final process, a process forming thepunched hole for defining said connecting through hole is omitted.Thereby, a useless punching process at the uppermost part of thelaminated core can be removed.

In the method of producing the laminated core according to theinvention, the laminated core is made of a motor core, and after the Bstep, the laminated core pieces are rotated. Herein, the “laminated corepieces are rotated” signifies that the cores are laminated at apredetermined sheet number, followed by rotating 360 degree/n (n:natural number). Thereby, even if the core pieces have uneven thickness,laminated core of fixed thickness may be formed.

In the method of producing the laminated core according to theinvention, the length (thickness) of the caulking projection is largerthan a full length of the connecting through hole for fitting thecaulking projection, while the caulking projection has a base portionwidening the width, and a front end portion of the caulking projectionis crushed (that is, widening the width) when laminating. Thereby, thecaulking projection and the connecting through hole are caughtaccurately, and the laminated core is made still stronger.

In the method of producing the laminated core according to theinvention, it is preferable that the connecting through hole is evenlydefined with a plurality of concaves at least at lower circumference.Thereby, the caulking projection is fitted at the part thereof in theconcave to check the caulking projection from getting out.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of schematically explaining the laminated core of afirst embodiment according to the invention;

FIG. 2 is a view of schematically explaining the laminated core of asecond embodiment according to the invention;

FIG. 3 is a view of schematically explaining concave portions defined inan inner circumference of the connecting through hole;

FIG. 4 is an explanatory view showing a conceptual structure of theconcave portions defined in the inner circumference of the connectingthrough hole of a modified example of the laminated core;

FIG. 5 is a perspective view of the laminated core of a third embodimentaccording to the invention;

FIG. 6 is a partially cross sectional view of a cut face P in FIG. 5;

FIG. 7 is a view of conceptually explaining the pressing apparatus forproducing the laminated core;

FIG. 8 is an explanatory view showing the punching process of thelaminated core; and

FIG. 9 is a schematically explanatory view showing the punching processfor a fourth embodiment according to the invention.

MOST PREFERRED EMBODIMENT OF THE INVENTION

With reference to the attached drawings, explanation will be made to thespecified embodiments for understanding the invention.

As seeing in FIG. 1, the laminated core 10 of the first embodiment ofthe invention has five sheets of core pieces 11 to 15 of substantiallyequal thickness between oppositely facing sides. A plurality of caulkingprojections 16 defined in the core piece 13 have a projecting lengthfrom one of the sides that is equal to twice the thickness of the corepiece 13, and are closely fitted in the connecting through hole 19defined by upper and lower connecting holes 17, 18 formed in the corepieces 11, 12. A plurality of caulking projections 20 defined in thecore piece 15 have a projecting length from one of the sides that isequal to twice the thickness of the core piece 15, and are closelyfitted in th connecting through hole 23 defined by upper and lowerconnecting holes 21, 22 formed in the core pieces 13, 14. The positionsof defining the respective caulking projections 16, 20 are arrangeddifferently viewing the core pieces 13, 15 in plan, and in moreparticular, the caulking projections 16, 20 are alternately disposedviewing in plan at a predetermined space. By the way, the actuallaminated core is ring shaped seeing in plan as shown in FIG. 5, but inFIG. 1 (also in FIG. 2), it is developed linearly.

As shown in FIG. 1, in this embodiment, the core piece 13 is used incommon to a lower laminated part 24 and an upper laminated part 25. Thelaminated core 10 has the lower laminated part 24 comprising the corepieces 11 to 13 and the upper laminated 25 comprising the core pieces 13to 15, and these laminated parts 24, 25 are alternately laminated tocompose the laminated core 10 of the predetermined thickness. Theconnecting hole 17 defined in the core piece 15 shows one part of aconnecting through hole for fitting therein a caulking projection of acore piece (not shown) at a further upper position.

The connecting holes 17, 18 forming the connecting through hole 19 andthe connecting holes 21, 22 forming the connecting through hole 23 arepunched holes formed by punching, and are rectangular shape viewing inplan. The connecting holes 18, 22 are respectively larger than theconnecting holes 17, 21. The connecting hole 17 and the connecting hole21 have the same configuration and the same dimension, while theconnecting hole 18 and the connecting hole 22 have the sameconfiguration and the same dimension.

The caulking projections 16, 20 fitting in the connecting through holes19, 23 have twice projecting length of thickness of the core pieces 11to 15, and the caulking projections 16, 20 have cross sectional shapesof substantially similar or the same rectangles. The caulkingprojections 16, 20 have base parts shaped in near trapezoid wideningwidth and gradually becoming narrower toward front ends. Further, thecaulking projections 16, 20 are formed in the core pieces 13, 15 atpredetermined pitch respectively coinciding with the positions of theconnecting through holes 19, 23. The caulking projections 16, 20 areclosely fitted in the connecting through holes 19, 23, and firmlyconnected to the core pieces 11 to 13 and the core pieces 13 to 15.

Production of the laminated core 10 comprises, as mentioned later,punching a bar steel of thin iron sheet (magnetic material) by a pressworking into core pieces 11 to 15 and laminating them in a die furnishedin a pressing apparatus. For laminating the core pieces 13, 15 providedwith the caulking projections 16, 20, the laminated core pieces areforcibly pressed by actuating a pressing mechanism (for example, ahydraulic cylinder, not shown) connected to later mentioned bottom sheetblocks 129, 130 (see FIG. 7) so as to mate front ends of the caulkingprojections 16, 20 to the respective connecting through holes 19, 23,thereby enabling to increase strength of the laminated core 10 . In thiscase, if projecting the caulking projections 16, 20 in a little rangfrom the bottoms of the core pieces 11, 13 (for example, the projectinglength is determined to be 1 to 10% of thickness of the core piece) andforcibly laminating the core pieces, thereby enabling to deform bywidening the free front ends of the caulking projections 16, 20 withinthe connecting holes 17, 21, so that it is possible to firmly secure thecaulking projections 16, 20 to the connecting through holes 19, 23.

In addition, since the caulking projections 16, 20 are nearlytrapezoidal viewing from the side, the sizes of the connecting holes 18,22 defined in the core pieces 12, 14 directly contacting the core pieces13, 15 defined with the caulking projections 16, 20, are determined tobe larger than the sizes of the connecting hole 17, 21 defined in thelower core pieces 11, 13. In such manners, the caulking projections 16,20 can be certainly inserted in the connecting through holes 19, 23 (thesame in the following embodiments).

Next, referring to FIG. 2, explanation will be made schematically e to alaminated core 27 of the second embodiment according to the invention.The laminated core 27 has core pieces 28 to 34 of substantially equalthickness, and are provided with caulking projections 35, 36 projectingdownward in core pieces 31, 34. The core pieces 28 to 30 are formed witha plurality of connecting through holes 40 comprising lower connectingholes 37, middle connecting holes 38 and upper connecting holes 39, andthe caulking projections 35 formed in the core pieces 31 are closelyfitted in the connecting through holes 40. Further, the core pieces 31to 33 are formed with a plurality of connecting through holes 44comprising lower connecting holes 41, middle connecting holes 42 andupper connecting holes 43, and the caulking projections 36 formed in thecore pieces 34 are closely fitted in the connecting through holes 44.Accordingly, in comparison with the laminated core 10 of the firstembodiment, the depth of the connecting through holes 40, 44 for fittingthe caulking projections 35, 36 is increased by an amount of one sheetof the core piece, and the length projecting downward of the caulkingprojections 35, 36 grows by three times of the thickness of the corepieces 31, 34, whereby the core pieces 28 to 31 form a lower laminatedpart 45, while the core pieces 31 to 34 form an upper laminated part.The laminated parts 45, 46 use the core piece 31 in common, and thelower and upper laminated parts 45, 46 are successive and alternatelylaminated to form the laminated core 27 of the predetermined thickness.

The caulking projections 35, 36 provided in the core pieces 31, 34 areprovided at different positions in plan, and are rectangular in crosssection and nearly trapezoidal viewing from the side. The lower andmiddle connecting holes 37, 38 for fitting caulking projection 35 (alsoas to the caulking projection 36) are rectangular seeing in plansimilarly to the cross sectional shape of the front part of the caulkingprojection 35. The upper connecting hole 39 for fitting the caulkingprojection 35 is rectangular in plan, and larger than the connectingholes 37, 38 for easily fitting the caulking projection 35. By the way,the connecting holes 37 to 39 forming the connecting through hole 40,the connecting holes 41 to 43 forming the connecting through hole 44,and the caulking projections 35, 36 are formed by the press working, andthe caulking projections 35, 36 are laminated in a metal die furnishedin the press working apparatus, and the whole laminated core 27 isproduced.

Further explanation will be made to the connecting holes 17, 18, 21 22for fitting the caulking projections 16, 20 shown in FIG. 1, and theconnecting holes 37 to 39 and 41 to 43 for fitting the caulkingprojections 35, 36 shown in FIG. 2. In the above embodiments, all theconnecting holes are rectangular (square), but may be circular,elliptical, or polygonal in agreement with shapes of the caulkingprojections. Also in this case, the connecting hole (the upperconnecting hole) formed immediately under the core piece with thecaulking projection is preferably larger in one side ranging between,e.g., 10 and 40%.

The lower connecting holes 17, 21 for fitting the caulking projections16, 20, and the lower and middle connecting holes 37, 38, 41, 42 forfitting the caulking projections 35, 36 are desirably formed withdiscrete concave parts/cut outs in the circumferences. This situationwill be explained by example of FIG. 3. The connecting hole 48 formed inthe core piece 47 represents the above mentioned connecting holes 17,21, 37, 38, 41, 42. The connecting hole 48 formed in the core piece 47represents the above mentioned connecting holes 17, 21, 37, 38, 41, 42.The connecting hole 48 is rectangular having discrete concaves (cutouts) 49, 50 in both length directions. In this case, the caulkingprojections (not shown) to be fitted therein are not formed with linearprojections to be fitted in the concaves/cut outs 49, 50, but if gettingthe caulking projection into the connecting hole 48 and forcing it, thecaulking projection bites at its one part into the concaves/cut outs 49,50, so that the caulking projection and the connecting hole 48 aresecurely fixed. Then, desirably, the caulking projection is projected ina little range (for example, 1 to 10% of the core piece, more preferably2 to 8%) from a lowermost connecting hole, whereby when laminating thecore pieces within the pressing apparatus (otherwise outside of thepressing apparatus), the caulking projection widens the width of itsfront portion by forcibly pressing up and down, so that is one partbites into the concaves/cut outs 49, 50. At this time, projectingcorners of the concaves/cut outs 49, 50 serve as hooks to check thecaulking projection from getting out, and play a role of strong caulkingconnection of the core piece. Thus, the concaves/cut outs are formed toprevent escape of the caulking projection in correspondence to theconnecting through holes 19, 23, 40, 41.

The above embodiment is concerned with the rectangular connecting hole,and FIG. 4 shows a case that a circular connecting hole 52 formed in acore piece 51 has discrete concaves/cut outs 53, 54 in both side of thecircumference thereof. Also in this case, if fitting the caulkingprojection into the connecting hole 52 and pressing it up and down, thecaulking projection bites at its part into concaves/cut outs 53, 54 tomake the caulking connection of the respective core pieces strong. Ashape of the caulking projection is nearly trapezoidal.

In a manner that the concaves/cut outs 49, 50, 53, 54 are formed in theconnecting holes 48 52, the caulking projection is restrained from freerotation or movement to consequently heighten the caulk-connectingstrength as the laminated core and secure stability of the shape.

In the above embodiments, the concaves/cut outs are two for oneconnecting hole, but the number is not limited. If the concaves/cut outsare more than three for one connecting hole, the concaves/cut outs aredesirably formed symmetrically with respect to an axis of the connectinghole, so that the core pieces is prevented from laterally moving duringlamination.

Further explanation will be made to a laminated core 61 of the thirdembodiment of the invention.

As shown in FIG. 5, the laminated core 61 is a stator core of a motor,an outer configuration is shaped in disc, and many core pieces 6 a, 6 b,6 c, 6 d, 6 e, 6 f, 6 g, 6 h, 6 i . . . (in the following, “6A”represent them) of substantially the same thickness are laminated viathe caulking connection. The respective core pieces 6A are defined witheight slots 62 equidistantly in the circumference direction, thereby todefine eight magnetic poles 63. The magnetic poles 63 have pole toothparts 64 at inside front ends for concentrating lines of magnetic forcethere. Therefore, by laminating the core pieces 6A, at the central partof the laminated core 61, a rotor core hole 65 is defined for receivingrotor cores surrounded by the magnetic poles 63 of the core pieces ofstator cores. Further, the laminated core 61 is formed with hollowranges 66 of slots 62 at the outer circumference side. Herein, thecaulking connection of the core pieces 6A is made via caulk-connectionportions 67 alternately formed at outsides (basic side) in a radiusdirection and at insides (front side) in the radius direction. In thefollowing, detailed explanation will be made to the structure of thelaminated core 61.

FIG. 6 shows a cross sectional structure seen when cutting the laminatedcore 61 at a cut P (FIG. 5). By the way, FIG. 6 shows the lower part ofthe cross sectional structure of the laminated core 61.

The core piece 6 a of a first layer is defined with a rectangular lowerconnecting hole (punched hole) 68, seeing in plan. The core piece 6 b isdefined with a rectangular upper connecting hole (punched hole) 69,seeing in plan, larger than the lower connecting hole 68. The corepieces 6 a, 6 b are laminated by meeting the axes of the lowerconnecting hole 68 and the upper connecting hole 69. Thereby, thelaminated core pieces 6 a, 6 b are formed with the connecting throughhole 70 composing one part of the caulk-connection portion 67. Inaddition, the core piece 6 c is provided with the caulking projection 71of a near-trapezoidal shape rectangular seeing in plan and having a longside of a base side seeing from the side, and provided with therectangular lower connecting hole 72 seeing in plan. By the way, theprojecting length of the caulking projection 71 from one of the sides ofthe associated core piece is substantially twice the thickness of therespective core pieces 6 a, 6 b. The core piece 6 c is laminated on thecore piece 6 b such that the axis of the caulking projection 71coincides with the axis of the connecting through hole 70. As a result,if loading in the laminating direction, the caulking projection 71 canbe fitted in the connecting through hole 70, so that the core pieces 6a, 6 c are caulk-connected to form a first laminated group 73.

The core piece 6 d is defined with a rectangular upper connecting hole74, seeing in plan, larger than the lower connecting hole 72. The corepieces 6 c, 6 d are laminated by meeting the axes of the lowerconnecting hole 72 and the upper connecting hole 74. Thereby, thelaminated core pieces 6 c, 6 d are formed with the connecting throughhole 75 composing one part of the caulk-connection portion 67. The corepiece 6 e is provided with the caulking projection 76 of anear-trapezoidal shape rectangular seeing in plan and having a long sideas a base side seeing from the side, and provided with the rectangularlower connecting hole 68 seeing in plan. By the way, the projectinglength of the caulking projection 76 is twice of thickness of therespective core pieces 6 c, 6 d. The core piece 6 e is laminated on thecore piece 6 d such that the axis of the caulking projection 76coincides with the axis of the connecting through hole 75. As a result,if loading in the laminating direction, the caulking projection 76 canbe fitted in the connecting through hole 75, so that the core pieces 6c, 6 d, 6 e are caulk-connected to form a second laminated group 77. Thefirst laminated group 73 and the second laminated group 77 use the corepiece 6 c in common, and when forming the second laminated group 77, thecaulking connection is made between the first laminated group 73 and thesecond laminated group 77 via the core piece 6 c.

Herein, the cross sectional areas in the upper sides of the connectingthrough holes 70, 75 are larger than those in the lower sides, and thecross sectional areas in the front ends of the caulking projections 71,76 are smaller than those in the basic ends, whereby the caulkingprojections 71, 76 can be securely inserted into the connecting throughholes 70, 75. The outer circumferences at the front sides of thecaulking projections 71, 76 can be closely contacted to the whole innercircumferences of the lower connecting holes 68, 72, while the outercircumferences at the basic sides of the caulking projections 71, 76 canbe closely contacted to the inner circumference s at the front ends ofthe lower connecting holes 69, 74. With the above mentioned structure,the respective core pieces 6 a, 6 b, 6 c, 6 d, 6 e are firmly connectedvia the caulk-connection.

Also as to the core pieces 6 f, 6 g, 6 h, 6 i . . . , a third laminatedgroup 78 is formed with the core pieces 6 e, 6 f, 6 g, while a fourthlaminated group 79 is successively formed with the core pieces 6 g, 6 h,6 i, and the caulk-connections are made between the respective laminatedgroups. As to the core pieces 6 f, 6 g, 6 h, 6 i . . . , beingstructurally the same in the lower connecting holes, the upperconnecting holes of the core pieces 6 b to 6 e, and the caulkingprojections, the same numerals are given them to omit detailedexplanations therefore.

FIG. 7 shows a schematic structure of the pressing apparatus 80 forproducing the laminated core (stator core) 61 of the present embodimentand rotor core being the same laminated core to be produced at the sametime. The respective core pieces of the stator core and the rotor coreare made with the same area (an area of forming core piece) of the samethin sheet bar material, and so the same numerals will be used to theemployed core pieces.

The pressing apparatus 80 is provided with a rotor core production areaat an upstream side and a stator core production area at a down streamside, and bar materials of magnetic materials (called as briefly “thinsheet 81” hereafter) from which the core pieces 6A are successivelypunched, are sent intermittently into the rotor core production are aand the stator core production area. An upper die 82 and a lower die 83for a punching process are communicated through pillars 84, and thelower die 83 is connected to a plunger (not shown) hydraulically drivenfor vertically moving the upper die 82. The thin sheet 81 is placedbetween the upper die 82 and the lower die 83, and is synchronized withthe pressing actuation of the upper die 82 and the lower die 83, and istransferred intermittently at desired speed.

The lower die 83 has a lower die set 85 connected with the plunger as anelevating mechanism and a die plate 86 provided on the upper side of thelower die set 85. The upper die 82 has an upper die set 87 securing theupper die 82 to a fixed frame (not shown) of the pressing apparatus 80,a punch plate 88 secured to the upper die set 87, and a stripper plate89 holding the thin sheet 81 together with the die plate 86. In therotor core production area, the punch plate 88 is provided, via a punchsupport plate 90, with punches 91, 92, 93, 94, 95 for processing a pilothole and rotor cores, as well as a rotor core-stamping punch 96. In thestator core production area, the punch plate 88 is provided, via a punchsupport plate 90, with punches 97, 98, 99, 100, 101 for processingstator cores, as well as a stator core stamping-punch 102. By the way,in this embodiment, the upper die 82 is stationary and the lower die 83moves vertically, but the invention is also applicable, vice versa, andto a case that the upper and lower dies move vertically as approachingor separating concurrently.

The stripper plate 89 is provided with punches 91 to 95 for processingthe pilot hole and the rotor cores, the rotor core-stamping punch 96,the stator core-processing punches 97 to 101, and the through-holes 103to 114 for passing a stator core-stamping punch 102. The die plate 86 isprovided with die holes 115 to 121 and 123 to 125 for inserting punchedpieces by the punches 91 to 95 and 97 to 101. The lower die set 85 isprovided with exhaust holes 126 continuing to the die holes 115 to 121and 123 to 125 for exhausting punched pieces.

Immediately under the stamping punch 96 of the rotor core of the lowerdie 83, a die hole 127 (a receiving part of a laminated core piece) isprovided for holding the core piece stamped by the punch 96 to composethe rotor core, and for laminating the core pieces in succession.Further, immediately under the stamping punch 102 of the stator core ofthe lower die 83, a die hole 128 is provided for holding the core piecestamped by the punch 102 to compose the stator core, and for laminatingthe core pieces 6A in succession. At the lower sides of the die holes127, 128, bottom plate blocks 129, 130 are provided for supporting thepunched core piece 6A, and are connected to a rotating mechanismfurnished in response to a pressing mechanism (not shown) and as needed,go down in response to lamination height of the core pieces, at the sametime effect pressure, and rotate the lamination of the core pieces asrequested, for example 45 degree.

With such a structure, for laminating the core pieces 6A in the dieholes 127, 128, while moving down the bottom plate blocks 129, 130, thelaminated core pieces are rotated at desired degree (45 degree) asrequested around the axes of the core pieces per predetermined sheets,and the respective core pieces 6A are carried out with caulk-connection,and thus the rotor laminated core and the stator laminated core ofdesired thickness are produced. The upper die set 87 is equipped with acontrol mechanism 131 for stopping actuation of the respective punches93, 94, 95, 99, 100, 101. The pressing apparatus 80 has been explainedas example as to the relation between the respective punches and the dieplates, showing parts of the punches and dies served to pressing of eachof the processes.

Following explanation will be made to productions of rotor core s andstator core s, using the pressing apparatus 80 shown in FIG. 7, inreference to FIG. 8 and Table 1.

TABLE 1 STAGE A B C D E F G H I J K L CAULK- CAULK- HOLDING HOLDING INGLAM- PUNCH- PUNCH- HOLDING HOLDING ING LAM- PILOT SHAFT THROUGH-THROUGH- PROJEC- INAT- ING ING THROUGH- THROUGH- PROJEC- INAT- STEPHOLES HOLES HOLE HOLE TION ING SLOTS SLOTS HOLE HOLE TION ING 1 (6a) ◯ 2(6b) ◯ (6a) ◯ 3 (6c) ◯ (6b) ◯ (6a) ◯ 4 (6d) ◯ (6c) ◯ (6b) (6a) 5 (6e) ◯(6d) ◯ (6c) ◯ (6b) ◯ (6a) ◯ 6 (6f) ◯ (6e) ◯ (6d) (6c) (6b) (6a) R 7 (6g)◯ (6f) ◯ (6e) ◯ (6d) ◯ (6c) ◯ (6b) (6a) ◯ 8 (6h) ◯ (6g) ◯ (6f) (6e) (6d)(6c) R (6b) ◯ (6a) ◯ 9 (6i) ◯ (6h) ◯ (6g) ◯ (6f) ◯ (6e) ◯ (6d) (6c) ◯(6b) ◯ (6a) ◯ 10 (6j) ◯ (6i) ◯ (6h) (6g) (6f) (6e) R (6d) ◯ (6c) ◯ (6b)(6a) 11 (6k) ◯ (6j) ◯ (6i) ◯ (6h) ◯ (6g) ◯ (6f) (6e) ◯ (6d) ◯ (6c) ◯(6b) ◯ (6a) 12 (6l) ◯ (6k) ◯ (6j) (6i) (6h) (6g) R (6f) ◯ (6e) ◯ (6d)(6c) (6b) (6a) R 13 (6m) ◯ (6l) ◯ (6k) ◯ (6j) ◯ (6i) ◯ (6h) (6g) ◯ (6f)◯ (6e) ◯ (6d) ◯ (6c) ◯ (6b) 14 (6n) ◯ (6m) ◯ (6l) (6k) (6j) (6i) R (6h)◯ (6g) ◯ (6f) (6e) (6d) (6c) R 15 (6o) ◯ (6n) ◯ (6m) ◯ (6l) ◯ (6k) ◯(6j) (6i) ◯ (6h) ◯ (6g) ◯ (6f) ◯ (6e) ◯ (6d) 16 (6p) ◯ (6o) ◯ (6n) (6m)(6l) (6k) R (6j) ◯ (6i) ◯ (6h) (6g) (6f) (6e) R HEREAFTER, STEPS 13 TO16 ARE REPEATED. (THERE IS A STEP FOR REMOVING LAMINATED CORE HAVING APREDETERMINED LAMINATION THICKNESS FROM DIE.) WHERE SYMBOL ◯ REPRESENTSPERFORMING A PROCESS, AND “R” REPRESENTS ROTATING A LAMINATED CORE 45°

As shown in FIG. 8, the pressing apparatus 80 has A to L stages. Thatis, there are equipped a stage A for processing pilot holes 132 fortransferring a thin sheet 81, a stage B for forming shaft holes 133 ofthe rotor core, a stage C for forming lower connecting holes, a stage Dfor forming upper connecting holes at positions rotating 45° withrespect to the position of the lower connecting hole, a stage E forforming the caulking projections, and a stage F for punching andlaminating the core pieces 6A composing the rotor core from the thinsheets 81 and laminating them.

Further, thepressing apparatus 80 is equipped with a stage G (processingfirst slots 62) for stepwise punching slots for the stator core,followed by punching the core pieces 6A for forming the rotor core, astage H (processing second slots 62), a stage I for forming lowerconnecting holes, a stage J for forming upper connecting holes atpositions rotating 45° with respect to the position of the lowerconnecting hole, a stage K for forming the caulking projections, and astage L for punching the core pieces 6A composing the rotor core fromthe thin sheets 81 and laminating them.

1st Step

As shown in Table 1, in the circumference of the core piece forming areawhere the core piece 6 a is formed in the stage A, the transferringpilot holes 132 are processed at both sides in the width direction ofthe thin sheet 81. Also in the following steps, since the pilot holes132 are formed in the stage A, explanation therefore will be omitted.The thin sheet 81 is sent to a next stage.

2nd Step

In the stage B, the shaft holes 133 are processed in the area where thecore pieces 6 a are formed. Also in the following steps, since the shaftholes 133 are formed in the core piece forming area of the stage B,explanation therefore will be omitted. The thin sheet 81 is sent to anext stage.

3rd Step

In the stage C, the lower connecting holes 68 are formed in the areawhere the core piece 6 a are formed, and the thin sheet 81 is sent to anext stage.

4th Step

The control mechanism 131 is operated to stop actuation of the punches93, 94. Consequently, in the stages C and D, the pressing work isstopped, and the thin sheet 81 is sent to a next stage.

5th Step

The control mechanism 131 is operated to stop actuation of the punch 95.In the stage C, the lower connecting holes 72 are formed in the areawhere the core piece 6 c is formed. In the stage D, the upper connectingholes 69 are formed in the area where the core piece 6 b is formed. Inthe stage E, the pressing work is stopped, and the thin sheet 81 is sentto a next stage.

6th Step

The control mechanism 131 is operated to stop actuation of the punches93 to 95. Consequently, in the steps C to E, the process is stopped. Inthe stage F, the core pieces 6 a are punched by the stamping punch 96,and laminated on the bottom plate block 129 within the die hole 127.Subsequently, the core pieces laminated on the bottom plate block 129are rotated 45° as needed. The thin sheet 81 is sent to a next stage.

7th Step

In the stage C, the lower connecting holes 72 are formed in the areawhere the core pieces 6 e are formed. In the stage D, the upperconnecting holes 74 are formed in the area where the core piece 6 d isformed. In the stage E, the caulking projections 71 are processed in thearea where the core piece 6 c is formed. Thereby, the lower connectingholes 72 and the caulking projection 71 are formed in the area where thecore piece 6 c is formed. In the stage F, the core pieces 6 b arepunched by the stamping punch 96, and laminated on the previouslylaminated core pieces 6 a within the die hole 127, so that theconnecting through hole 70 is formed (the A Step of the invention) Inthe stage G, the first slot 62 is processed by the punch 97 in the areawhere the core piece 6 a is formed. In the following step, the stage Gis processed as to the area where the core pieces are formed, and sodescription therefore is omitted. The thin sheet 81 is sent to a nextstage.

8th Step

The control mechanism 131 is operated to stop actuation of the punches93 to 95. Consequently, in the stages C to E, the process is stopped. Inthe stage F, the core pieces 6 c are punched by the stamping punch 96,and laminated on the previously laminated core pieces 6 b within the diehole 127, and the caulking projection 71 goes into the connectingthrough hole 70, so that the caulking coupling is generated to form thefirst laminated group 73 (the B Step of the invention). Subsequently,the first group 73 is rotated 45°. In the stage H, the second slot 62 isprocessed by the punch 98 in the area where the core piece 6 a is formed(in the following, explanation for the same process will be omitted).Thereby, all the slots 62 are accomplished in the area where the corepiece 6 a is formed. The thin sheet 81 is sent to a next stage.

9th Step

In the stage C, the lower connecting holes 72 are formed in the areawhere the core pieces 6 g are formed. In the stage D, the upperconnecting holes 69 are formed in the area where the core piece 6 f isformed. In the stage E, the caulking projections 76 are processed in thearea where the core piece 6 e is formed. Thereby, the lower connectinghole 68 and the caulking projection 76 are formed in the area where thecore piece 6 e is formed. In the stage F, the core pieces 6 d arepunched by the stamping punch 96, and laminated on the previouslylaminated core pieces 6 c within the die hole 127, so that theconnecting through hole 75 is formed (the C Step of the invention). Inthe stage I, the lower connecting hole 68 is formed in the area wherethe core piece 6 a is formed. The thin sheet 81 is sent to a next stage.

10th Step

The control mechanism 131 is operated to stop actuation of the punches93 to 95, 99 and 100. In the stages C to E, the process is stopped. Inthe stages F, the core pieces 6 e are punched by the stamping punch 96,and laminated on the previously laminated core pieces 6 d within the diehole 127, and the caulking projection 76 goes into the connectingthrough hole 75, and at the same time the caulking coupling is generatedto form the second laminated group 77 (the B Step of the invention).Subsequently, the bottom plate block 129 is rotated 45° if necessary. Inthe steps I and J, the process is stopped. The thin sheet 81 is sent toa next stage.

11th Step

The control mechanism 131 is operated to stop the actuation of the punch101. Herein, since the process in the step A to F is the same as that ofthe stages A to F, detailed explanation will be omitted. In the stage I,the lower connecting holes 72 are formed in the area where the corepiece 6 c is formed. In the stage J, the upper connecting hole 69 isformed in the area where the core piece 6 b is formed. In the stage K,the pressing work is stopped, and the thin sheet 81 is sent to a nextstage.

12th Step

The control mechanism 131 is operated to stop actuation of the punches93 to 95, 99 to 101. Herein, since the process in the stages A to F (inparticular, A to G) is the same as that of the stages A to F of the 8thstep, detailed explanation will be omitted. In the stages I to K, theprocess is stopped. In the stages L, the core pieces 6 a are punched bythe stamping punch 102, and laminated on the bottom plate block 130within the die hole 128. Subsequently, the bottom plate block 129 isrotated 45° if necessary. In the stages I and J, the process is stopped.The thin sheet 81 is sent to a next stage.

13th Step

Since the process in the stages A to H is the same as that of the stagesA to H of the 9th step, detailed explanation will be omitted. In thestage I, the lower connecting holes 68 are formed in the area where thecore piece 6 e is formed. In the stage J, the upper connecting hole 74is formed in the area where the core piece 6 d is formed. In the stageK, the caulking projection 71 is processed in the area where the corepiece 6 c is formed. Thereby, the lower connecting hole 72 and thecaulking projection 71 are formed in the area where the core piece 6 cis formed. In the stage L, the core pieces 6 b are punched by thestamping punch 102, and laminated on the previously laminated corepieces 6 a within the die hole 128, so that the connecting through hole70 is formed (the A Step of the invention), and the thin sheet 81 issent to a next stage.

14th Step

The control mechanism 131 is operated to stop the actuation of thepunches 93 to 95, 99 to 101. Herein, since the process in the stages Ato I is the same as that of the stages A to I of the 10th step, detailedexplanation will be omitted. In the stages J and K, the process isstopped. In the stages L, the core pieces 6 c are punched by thestamping punch 102, and laminated on the previously laminated corepieces 6 b within the die hole 128, and the caulking projection 71 goesinto the connecting through hole 70, and at the same time the caulkingcoupling is generated to form the first laminated group 73 (the B Stepof the invention). Subsequently, the bottom plate block 129 is rotated45° if necessary, and the thin sheet 81 is sent to a next stage.

15th Step

Since the process in the stages A to J is the same as that of the stagesA to J of the 11th step, detailed explanation will be omitted. In thestage K, the caulking projection 76 is processed in the area where thecore piece 6 e is formed. Thereby, the lower connecting hole 68 and thecaulking projection 76 are formed in the area where the core piece 6 eis formed. In the stage L, the core pieces 6 d are punched by the punch102, and laminated on the previously laminated core pieces 6 c withinthe die hole 128, so that the connecting through hole 75 is formed (theC step of the invention), and the thin sheet 81 is sent to a next stage.

16th Step

The control mechanism 131 is operated to stop the actuation of thepunches 93 to 95, 99 to 101. Herein, since the process in the stages Ato K is the same as that of the stages A to K of the 12th step, detailedexplanation will be omitted. In the stages L, the core pieces 6 e arepunched by the punch 102, and laminated on the previously laminated corepieces 6 d within the die hole 128, and the caulking projection 76 goesinto the connecting through hole 75, and at the same time the caulkingcoupling is generated to form the first laminated group 77 (the B stepof the invention). At this time, the caulking coupling is also carriedout between the first laminating sheets group 73 and the secondlaminating sheets group 77. Subsequently, the bottom plate block 130 isrotated 45°, and the thin sheet 81 is sent to a next stage.

17th Step and the Following

In the 17th step and the following, the 13th to 16th steps are repeated.Incidentally, in the die holes 127, 128, the laminated core 61 graduallyincreases thickness each time when the caulking coupling is generated,and so the bottom plate blocks 129, 130 are slowly moved down by use ofa pressure mechanism (for example, a hydraulic cylinder, not shown).When laminating until the predetermined thickness, the laminated core isremoved under the die holes 127, 128. A final process, in the laminatedcore of the rotor, is finished by laminating the core piece defined withthe caulking projections (the stage F). The laminated core of the statoris finished by laminating the core piece defined with the caulkingprojections (the stage L). In this case, holes (the lower connectingholes) punched in the core piece of the final stage may be omitted.

By the way, in this embodiment, in order that the positions defined withthe caulking projections are not overlapped by the core layersneighboring up and down (for example, the first laminated sheets group73, the second laminated sheets group 77, and the third laminated sheetsgroup 78), the core pieces 6 c, 6 e, 6 g defined with the caulkingprojections are laminated, followed by rotating (i.e., of thelamination) the laminated core pieces at the predetermined angle (45°),but, instead, it is available that the stage number of punching processis increased so as to select the punches to be served per each of thecore pieces, and change the |s and the positions of the caulkingprojections to be fitted therein per each of the core layers neighboringup and down, so that the laminated core is produced. In such a case, therotation of the laminated core pieces within the die hole is not carriedout. Also in this case, it is possible to furnish a plurality ofselected punches in one stage for reducing the stage number of pressingprocess.

Successively, referring to FIG. 9, explanation will be made to theproduction of the laminated core in the fourth embodiment.

In the stage A, the thin sheet 143 of the magnetic material punched withfour pilot holes 141, 142 is formed with the core pieces of a rotor coreand a stator core in area (called as the “core piece forming area”)surrounded with the four pilot holes 141, 142. The core piece formingareas surrounded with the pilot holes 141, 142 are defined with shaftholes (axis holes) in the stage B. In the next stage C, the lowerconnecting holes of the four connecting through holes 145 are defined(the punched holes). The four connecting through holes 145 are arrangedat the angular positions of 0°, 90°, 180°, and 270° with respect to thestandard being the center of the core piece forming area. As to the corepiece forming area (the thin sheet) sent to the stage C, the upperconnecting holes forming the connecting through holes 145 are formed,while as to the subsequently sent thin sheet 143, the lower connectingholes are formed which form the connecting through holes 145 of the sameradius at the position of 45 degree of the same radius, with respect tothe caulking projections for fitting in the connecting through holes 145as well as the respective connecting through holes 145. By the way, inthe stage C, each time when forming different connecting holes andcaulking projections, different punches and dies are used.

The next stage D is for laminating the rotor core, and there arelaminated, at first, the core pieces 146 of the rotor core defined withthe lower connecting holes of the connecting through holes 145,secondly, the core pieces 146 of the rotor core defined with the upperconnecting holes of the connecting through holes 145, and thirdly, thecore pieces defined with the lower connecting holes of the connectingthrough holes at the position of 45° with respect to the caulkingprojection. At the step of finishing this lamination, the rotation isdone toward the predetermined position of 45° in order that the caulkingprojection fitted in the connecting through hole 145 comes to the shownposition of the connecting through hole 145.

Subsequently, the core pieces 146 of the rotor core defined with theupper connecting holes are laminated, and further thereon, the corepieces defined with the lower connecting holes are laminated at theposition of 45° with respect to the caulking projection, and thelaminated core pieces are rotated toward the predetermined position of45°. Passing through these steps, the laminated core of the rotor isformed at the predetermined height.

The core piece forming area where the rotor core has been punched outare punched with the slots 147 forming the magnetic poles of the statorcore in the stage E, and in the next stage F, the core piece formingarea of the thin sheet successively sent are formed with the upper andlower connecting holes (punched holes) forming the four connectingthrough holes 148 outside and the four connecting through holes 149inside as well as the caulking projections. The stage G is the area forlaminating the stator core, and there are laminated, at first, the corepieces 150 of the stator core defined with the lower connecting holes,secondly, the core pieces 150 of the stator core defined with the upperconnecting holes, and thirdly, the core pieces 150 of the stator coredefined with the caulking projections for fitting the |s formed with theupper and lower connecting holes. The core piece defined with thecaulking projections is formed with the lower connecting holes (eight)at the 45° positions. When laminating the core piece 150 of the statorcore formed with the caulking projections, the die supporting thelaminated core is rotated in the predetermined direction of 45°(rotation of the lamination), and as shown in the illustrated stage G,the lower connecting holes forming the lower connecting holes arepositioned at the place where the caulking projection has been present,and so the core pieces 150 of the stator core formed with the connectingholes are successively laminated thereon, and the core pieces 150 of thestator core formed with the connecting holes are successively laminatedfurther thereon. As laminating the rotor core, by repeating the abovesteps, the laminated core of the stator core is accomplished.

In the production of the laminated core of the fourth embodiment, thepunches and the corresponding dies are changed in the stage C and thestage F for forming the plurality of connecting through holes andcaulking projections, but as shown in the third embodiment, it isnaturally possible to divide them into the plural stages and perform thepressing work.

In the precedent embodiments, the caulking projection is nearlytrapezoidal, and may be nearly multi-trapezoidal in coinciding to sizesof the connecting through holes defined in the core pieces of therespective layers.

Further, the invention is not limited to the above mentionedembodiments, and so far as the subject matter of the invention is notchanged, improvements or modifications are of course available. Theinvention is applicable to the cases of composing the laminated core bycombination of the above 1st to 4th embodiments or of producing it.

INDUSTRIAL APPLICABILITY

As to the embodiment of the invention, the caulking projections definedin one sheet of the core piece are fitted in the connecting throughholes formed in a plurality of core pieces, so that the caulkingcouplings are provided to laminate and combine many sheets of corepieces, and the caulking couplings neighboring up and down are changedin the lamination-forming positions. Accordingly, even if thickness ofthe core piece is small, the caulking projections are fitted in theconnecting through holes defined in a plurality of core pieces, enablingto secure the fitting depth of the caulking projection, whereby theset-up core piece heightens strength.

In the embodiment of the invention, the caulking projection has a baseportion reducing the width as going in a front end direction, and, if,among the connecting through holes formed in said plural core pieces,the connecting through hole of the core piece immediately under saidcore piece formed with the caulking projection has the width wideningthan said width of said caulking projection, the caulking projectionseasily fit into the core pieces immediately under the core piecesdefined with the caulking projections, and after the core goes a littlethereinto, the connecting through hole (the upper connecting hole) ofthe core is a guide for the caulking projections and the caulkingprojection is difficult to cause buckling or bending, so that defectedproducts are extremely decreased.

In the embodiment of the invention, when the connecting through holeformed in the core piece is partially defined at circumference withconcaves, the caulking projection partially goes into the core atlamination, and the caulking strength increases to make the laminatedcore still stronger.

In the laminated core of the invention, when the concaves are two ormore, and the respective concaves are defined symmetrically with respectto the axis of the connecting through hole, the caulking projection isdifficult to generate bias, and as a result, the core causes nodivergence in lamination, and bad products are reduced.

In the laminated core of the invention, when the caulking projection isshaped as nearly trapezoidal or nearly multi-trapezoidal viewing fromthe side thereof, the corner of the caulking projection bites into theconnecting through hole, or no twist is generated in the caulkingprojection. Therefore, the laminated core increases strength, and thecaulking projection is difficult to cause twist.

In the laminated core of the invention, when the caulking projection hasa front end portion widening the width owing to pressure, the caulkingprojection and the connecting through hole are caught accurately, sothat the stronger laminated core can be produced.

A method of producing laminated cores according to the invention, issuch a method where caulking projections and connecting through holesare formed in many sheets of core pieces punched in magnetic thin sheetsby a pressing apparatus, and caulking connection is performed whilelaminating these core pieces, and comprises: an A step of punching theplural sheets of core pieces formed with the connecting through holes inthe magnetic thin sheets by means of the pressing apparatus, a B step offorming caulking projections passing until the bottoms of the connectingthrough holes formed in the plural sheets of core pieces laminated inthe precedent step, and laminating core pieces formed, in upper places,with punched holes forming parts of connecting through holes for fittingnew caulking projections formed in places different from those of saidcaulking projections, and a C step of laminating core pieces formed withpunched holes to be parts of the connecting through holes formed bymeeting axes to said punched holes of said core pieces laminated in theB step, and forming plural sheets of core pieces defined with theconnecting through holes together with said core pieces laminated in theB step, wherein the B step and the C step are repeated to form the corelaminated at a predetermined thickness in said B step as a finalprocess. Thereby, it is possible to produce the laminated core by use ofthe pressing apparatus, changing places, where the caulking projectionsbite into a plurality of core pieces, in the laminating directionneighboring in the vertical direction.

In the method of producing the laminated core according to theinvention, in the B step as said final process, if a process forming thepunched hole for defining said connecting through hole is omitted, auseless punching process at the uppermost part of the laminated core canbe removed, so that the outer appearance is heightened.

In the method of producing the laminated core according to theinvention, if the laminated core is made of a motor core, and after theB step, the laminated core pieces are rotated, even if the cores haveuneven thickness, the laminated core of fixed thickness may be formed.

In the method of producing the laminated core according to theinvention, if the length (thickness) of the caulking projection islarger than a full length of the connecting through hole for fitting thecaulking projection, while the caulking projection has a base portionwidening the width, and a front end portion of the caulking projectionis crushed (that is, widening the width) when laminating, the caulkingprojection and the connecting through hole are caught accurately, andthe laminated core is made still stronger.

In the method of producing the laminated core according to theinvention, if the connecting through hole is evenly defined with aplurality of concaves at least at lower circumference, the caulkingprojection is fitted at the part thereof in the concave to check thecaulking projection from getting out.

1. A laminated core comprising: a plurality of core pieces including: a)a first core piece having a thickness between first and secondoppositely facing sides, the first core piece made from metal and formedwith caulking projections each having a projecting length extending fromone of the oppositely facing sides; and b) a second core piece made frommetal and formed with connecting through holes that fit said caulkingprojections, said second core piece laminated under said first corepiece, wherein each of the connecting through holes has a circumferenceat which at least one discrete cut out is formed, wherein the caulkingprojections on the first core piece are forced into the first connectingthrough holes so that a part of each of the caulking projections isdeformed by biting into one of the discrete cut outs and the caulkingprojections are securely fixed in the connecting through holes tothereby maintain the first core piece and the second core piecetogether.
 2. The laminated core as set forth in claim 1, wherein thecaulking projections on the first core piece have a base portion havinga width that is reduced going in a front end direction, the plurality ofcore pieces comprises a third core piece made from metal and formed withconnecting through holes that fit said caulking projections on the firstcore piece, the third core piece immediately under the first core piece,the connecting through holes in the third core piece having a widthwider than said width of said caulking projections on the first corepiece.
 3. The laminated core as set forth in claim 1, wherein theconnecting through holes in the second core piece each has a first axis,a plurality of the cut outs are formed at the circumference of each ofthe connecting through holes in the second core piece, and the cut outsare positioned symmetrically to each other with respect to the firstaxis for each of the connecting through holes.
 4. The laminated core asset forth in claim 1, wherein one of the caulking projections is shapedas substantially trapezoidal or substantially multi-trapezoidal viewingfrom a side thereof.
 5. A laminated core comprising: a plurality ofmetal core pieces laminated together and each having a thickness betweenfirst and second oppositely facing sides, said plurality of core piecesincluding at least first and second core pieces respectively located inupper and lower positions and a third core piece that is laminatedbetween the first and second core pieces, the first and second corepieces each formed with caulking projections each having a lengthprojecting from one of the sides of the first and second core pieces andconnecting through holes at positions different than where the caulkingprojections are located, the third core piece formed with connectingthrough holes that fit said caulking projections on the first corepiece, the projecting lengths of the caulking projections on the firstcore piece greater than the thickness of the third core piece so thatthe caulking projections on the first core piece can pass fully throughthe connecting through holes in the third core piece before anydeformation of the caulking projections and fit to the connectingthrough holes in the second core piece, wherein the caulking projectionson the first core piece are deformed by widening within the connectingthrough holes in the second core piece without extending a significantdistance from the connecting through holes in the second core piece tofirmly secure the caulking projections on the first core piece in theconnecting through holes in the second core piece to thereby preventwithdrawal of the caulking projections on the first core piece from theconnecting through holes in the second and third core pieces.
 6. Thelaminated core as set forth in 5, wherein one of the caulkingprojections has a free front end portion with a width that is widened bydeformation within a connecting through hole.
 7. The laminated core asset forth in claim 5 wherein each of the connecting through holes formedin one of the second and third core pieces has a circumference at whichat least one discrete cut out is formed, and the caulking projections onthe first core piece extend and bite into the discrete cut outs in theone of the second and third core pieces.
 8. The laminated core as setforth in claim 1, wherein a plurality of the caulking projections isshaped as substantially trapezoidal or substantially multi-trapezoidalviewing from a side thereof.
 9. The laminated core as set forth in claim3, wherein one of the caulking projections is shaped as substantiallytrapezoidal or substantially multi-trapezoidal viewing from a sidethereof.
 10. The laminated core as set forth in claim 5, wherein one ofthe caulking projections is shaped as substantially trapezoidal orsubstantially multi-trapezoidal viewing from a side thereof.
 11. Thelaminated core as set forth in claim 1 wherein the thicknesses of atleast two of the core pieces are approximately the same.
 12. Thelaminated core as set forth in claim 1 wherein the first and second corepieces have flat facially engaging surfaces respectively around thecaulking projections and connecting through holes.
 13. The laminatedcore as set forth in claim 1 wherein one of the caulking projections onthe first core piece is compressed and thereby widened to cause the oneof the caulking projections to bite into one of the discrete cut outs.14. The laminated core as set forth in claim 1 wherein the connectingthrough holes each has an axis and the first core piece has a connectingthrough hole that fits a caulking projection of an upper core piecelaminated to and on top of the first core piece, the connecting throughhole in the first core piece located at a place that is different from aplace at which one of the caulking projection is formed in the firstcore piece, as viewed along the through hole axes.
 15. The laminatedcore as set forth in claim 1 wherein the discrete cut outs each servesas a hook to check a caulking projection from separating from thediscrete cut outs.
 16. The laminated core as set forth in claim 5,wherein a plurality of the caulking projections is shaped assubstantially trapezoidal or substantially multi-trapezoidal viewingfrom a side thereof.